I had to set classTreatment to Ignore since the class in "Iris" is discrete with three values and cannot be converted into two or three dummy variables (orange does not allow more than one dependent variable).

The continuizer does not return a scaled data but a domain description with attributes that are scaled versions of the original attributes (using the span of their values in the original data). To do the scaling, you then construct a new example table from the old one with the new domain, as the last line does.